1. Field of the Disclosure
The present disclosure relates generally to an apparatus and a method for determining the orientation of randomly arranged birefringent fibers, such as for example textile fibers and hair.
2. Background Art
Polarization imaging is being used in many applications. In passive imaging, where the illumination is not controlled, i.e., not actively polarized, polarization imaging can be used, for example, to enhance the contrast between human made objects that have a strong polarization signature from the natural background. It also provides information on the shape of the objects. Further, polarization imaging conveniently allows for the detection of water or mud surfaces thanks to the strong polarization signature of water.
In active imaging, where the illumination is controlled and polarized, polarization imaging can be used to study light scattering. In fact, two-state polarization allows to easily separate the surface scattering from the volume scattering. Specular reflections and color information can therefore be separated, thus providing information on the structure of the studied objects.
Polarization imaging is applied, for example, in the cosmetic industry where studying the visual appearance (of the skin, the hair, etc.). Polarization imaging can be used as a tool to improve formulation for both hair and skin care products, such as styling products, for example by visualizing the improvement of the structure and appearance of hair once the product is applied.
For determining the orientation of birefringent fibers, such as hair, methods using image processing are known. These methods apply a Fourier transform to the fiber images so as to obtain the orientation of the neutral axis of the fibers. However, according to these methods assumptions have to be made about the light that is internally reflected inside the fibers. Furthermore, in order to obtain the orientation of their neutral axis, the fibers all have to have the same orientation.
Therefore, there is a need to provide an improved method and an improved apparatus for the orientation determination of randomly arranged birefringent fibers which are capable of determining the orientation of the fibers, independently from the orientation thereof.